Power generation system and inverter for feeding power into a three-phase grid

Abstract

A power generation system for feeding electrical power from a generation unit into a three-phase grid via three AC terminals is disclosed. The system includes a relay arrangement for disconnecting the system from the grid having at least three relays. Each of the three relays includes a control coil and two switching contacts operated by the corresponding control coil. Each of the AC terminals is connectable to the grid via a first and a second switching contact, each of which is assigned to a different one of the relays. Further disclosed are a relay arrangement and an inverter with a relay arrangement.

What we claim is: 
     
      
       1. A power generation system for feeding electrical power from a generation unit into a three-phase grid via three AC terminals, the system comprising: 
       
         a relay arrangement for disconnecting the system from the grid, wherein: 
         the relay arrangement comprises at least three relays, 
         each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and 
         each of the AC terminals is connectable to the grid via a first switching contact and a second switching contact, wherein each of the first switching contact and the second switching contact is within a different one of the relays. 
       
      
     
     
      
       2. The system of  claim 1 , wherein the system further comprises an inverter configured to receive the electrical power from the generation unit and convert a DC power into an AC power. 
      
     
     
      
       3. The system of  claim 2 , wherein the inverter is a photovoltaic inverter. 
      
     
     
      
       4. The system of  claim 3 , wherein the generation unit comprises photovoltaic generators. 
      
     
     
      
       5. The system of  claim 2 , wherein the inverter is a transformerless inverter. 
      
     
     
      
       6. The system of  claim 1 , wherein each of the relays is separately operable by a corresponding relay driver. 
      
     
     
      
       7. The system of  claim 6 , wherein each relay driver is configured to operate the corresponding relay only upon presence of a setting signal of a control unit and an interrupt signal of a watchdog arrangement. 
      
     
     
      
       8. The system of  claim 7 , wherein the control unit is monitored by the watchdog arrangement. 
      
     
     
      
       9. The system of  claim 7 , wherein each relay driver is configured to be monitored by a test signal of the control unit. 
      
     
     
      
       10. The system of  claim 9 , wherein control signals for the control coils are interrupted upon presence of the test signal, a duration of the interruption is selected to be short enough to prevent an opening of switches for disconnecting the system from the grid, and a response of the control coils to the test signal is evaluated by the control unit. 
      
     
     
      
       11. The system of  claim 1 , wherein the relay arrangement comprises automatic switches for preventing unintended connection of the system to the grid. 
      
     
     
      
       12. The system of  claim 1 , wherein the relay arrangement is integrated into a housing of the system. 
      
     
     
      
       13. The system of  claim 1 , wherein the relays are arranged on a circuit board. 
      
     
     
      
       14. An inverter for converting a DC power into an AC power provided to a three-phase grid via three AC terminals, the inverter comprising: 
       
         a relay arrangement for disconnecting the inverter from the grid, wherein: 
         the relay arrangement comprises at least three relays, 
         each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and 
         each of the AC terminals is connectable to the grid via a first switching contact and a second switching contact, wherein each of the first switching contact and the second switching contact is within a different one of the relays. 
       
      
     
     
      
       15. The inverter of  claim 14 , wherein the inverter is a photovoltaic inverter. 
      
     
     
      
       16. The inverter of  claim 14 , wherein the relay arrangement is integrated into a housing of the inverter. 
      
     
     
      
       17. A relay arrangement for disconnecting an inverter from a three-phase grid with three active conductors, the relay arrangement comprising: 
       
         at least three relays, wherein: 
         each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and 
         each switching contact is connected to another switching contact that is within a different one of the relays. 
       
      
     
     
      
       18. The relay arrangement of  claim 17 , wherein the relay arrangement further comprises automatic switches for preventing unintended connection of the inverter to the grid. 
      
     
     
      
       19. The relay arrangement of  claim 17 , wherein each of the relays is separately operable by a corresponding relay driver. 
      
     
     
      
       20. The relay arrangement of  claim 19 , wherein each relay driver is configured to operate the corresponding relay only upon presence of a setting signal of a control unit and an interrupt signal of a watchdog arrangement. 
      
     
     
      
       21. The relay arrangement of  claim 20 , wherein the control unit is monitored by the watchdog arrangement. 
      
     
     
      
       22. The relay arrangement of  claim 20 , wherein each relay driver is configured to be monitored by a test signal of the control unit. 
      
     
     
      
       23. The relay arrangement of  claim 22 , wherein control signals for the control coils are interrupted upon presence of the test signal, a duration of the interruption is selected to be short enough to prevent an opening of switches for disconnecting the inverter from the grid, and a response of the control coils to the test signal is evaluated by the control unit. 
      
     
     
       24. A power generation system for feeding electrical power from a generation unit into a three-phase grid via three AC terminals, the system comprising:
 inverter circuitry comprising:
 DC input terminals configured to receive DC power; 
 three AC terminals configured to provide three-phase AC power; 
 a bridge configured to convert the DC power into the three-phase AC power and connected between the DC input terminals and the three AC terminals; 
 a first electrical path connecting a first leg of the bridge to a first AC terminal of the AC terminals; 
 a second electrical path connecting a second leg of the bridge to a second AC terminal of the AC terminals; and 
 a third electrical path connecting a third leg of the bridge to a third AC terminal of the AC terminals; 
   a relay arrangement configured to disconnect the inverter from three active conductors of the three-phase grid, the relay arrangement comprising exactly three relays and comprising;   a first output terminal connected to a first input terminal of the relay arrangement via a first switching contact and a second switching contact, wherein the first switching contact is directly connected to the first input terminal, wherein the second switching contact is directly connected to the first output terminal, and wherein the first and second switching contacts are directly connected to each other and the first input terminal is connected to the first AC terminal;   a second output terminal connected to a second input terminal of the relay arrangement via a third switching contact and a fourth switching contact, wherein the third switching contact is directly connected to the second input terminal, wherein the fourth switching contact is directly connected to the second output terminal, and wherein the third and fourth switching contacts are directly connected to each other and the second input terminal is connected to the second AC terminal; and   a third output terminal connected to a third input terminal of the relay arrangement via a fifth switching contact and a sixth switching contact, wherein the fifth switching contact is directly connected to the third input terminal, wherein the sixth switching contact is directly connected to the third output terminal, and wherein the fifth and sixth switching contacts are directly connected to each other and the third input terminal is connected to the third AC terminal,   wherein the first and sixth switching contacts are commonly operable by a first control coil of a first relay,   wherein the second and third switching contacts are commonly operable by a second control coil of a second relay,   wherein the fourth and fifth switching contacts are commonly operable by a third control coil of a third relay,   wherein each of the first, second and third relays comprises a control coil and has exactly two switching contacts operated by the corresponding control coil,   wherein the first output terminal, second output terminal and third output terminals are connected to the three-phase grid, and   wherein the relay arrangement is integrated into a housing of the system.